Method of continuous casting

ABSTRACT

Apparatus for a process of continuously casting metals by passing a metal core member upwardly through a container of molten metal, and thereby accreting and solidifying molten metal on the core member; and, a method of continuously casting metals. The apparatus comprises a molten metal container or crucible with an entry port in its bottom wall for the passage of the core member. Positioned within the entry port is a bushing member of molybdenum alloyed with titanium and zirconium, and in the method the core member is passed through the molybdenum alloy bushing.

United States Patent [1 1 Carrara 1 Dec.2, 1975 METHOD OF CONTINUOUSCASTING [75] Inventor:

[73] Assignee'. General Electric Company, New

York, N.Y.

[22] Filed: June 28, 1973 [21] Appl. No.: 374,760

Marcel V. Carrara, Seymour, Conn.

[52] US. Cl. 427/431; 164/86; 308/241;

427/295; 427/329 [5 l] Int. Cl. C23C 1/00 [58] Field of Search 117/114R; 118/405, 404,

[56] References Cited UNITED STATES PATENTS 3,269,825 5/1963 Vordahl75/l75.5 3,424,130 1/1969 Byrnes ct a1. 118/405 3,610,204 10/1971Corrigan 118/405 3.709,722 l/l973 Corrigan 117/114 R PrimaryExaminerMayer Weinblatt Assistant Examiner-Edith R. Buffalow Attorney,Agent, or FirmR. G. Simkins; P. L. Schlamp; F. L. Neuhauser 157 7ABSTRACT 3 Claims, 2 Drawing Figures US. Patent Dec. 2, 1975 METHOD OFCONTINUOUS CASTING BACKGROUND OF THE INVENTION This invention relates toan improvement in apparatus and method for continuous metal casting, orthe socalled dip forming process of metal casting. The apparatusincludes a crucible or refractory container for molten metal which isprovided with an entry port or orifice for the introduction and passageof a core member into the crucible or container and through the moltenmetal contained therein. A bushing member of refractory metal isinserted in the entry port or orifice to provide a relatively wearresistant seal about the moving core member.

The dip forming process of continuously casting by means of passing acore member upwardly through a crucible of molten metal, and apparatustherefor, is the subject of many prior US. patents, including:

The disclosures of these US. patents are incorporated herein byreference.

The dip forming process of continuously casting as heretofore practicedand provided for by prior art apparatus, incurred a serious defect inthe form of the introduction of contaminating bodies of foreign metal ormaterial into the cast product. The most common source of such bodies offoreign metal or material within the cast product, referred to in thisart as inclusions", appears to be the bushing member in the entry portin the crucible bottom which is utilized as a close fitting seal aboutthe core member as it moves therethrough into the molten contents of thecrucible. It appears that particles separate from the bushing member,which is typically composed of a hard refractory material such assintered molybdenum, and penetrate the core member moving therethrough.These embedded foreign particles or bodies in the core member are thencarried through the casting operation wherein they may become completelyenveloped within the cast product.

The presence of particles of any foreign metal or other material fromthe bushing member, or whatever the source, in cast metal productscomprises a substantial detriment in subsequent metal working operationssuch drawing, rolling, forging, extruding, and the like, and in theproducts derived therefrom. Moreover, the dip forming process ofcontinuously casting is primarily utilized in commercial manufacturingoperations for the production of copper rod for use in drawingelectrical conducting wires. The existence of any foreign particles, andespecially of a very hard material such as molybdenum, in copper rodspresents an especially serious impediment in the drawing of wireinasmuch as their presence causes frequent breakages in the extendingstrands, thereby disrupting the production system, or resulting inweakened and inferior wire products. Also, the passage of relativelyhard particles such as molybdenum entrained in copper through drawingdies or reducing rolls, and other metal working apparatus, is

detrimental to such equipment.

SUMMARY OF THE INVENTION This invention comprises an improvement in theapparatus and method for carrying out a continuous metal casting or dipforming process comprising passing a core member upwardly through acrucible containing molten metal, which substantially eliminates theoccurrence of entrained particles or bodies of foreign metal ormaterial, so-called inclusions, within the cast products.

The improvement of this invention includes provid ing a bushing memberinsert for the crucible entry port composed of molybdenum alloyed withminor amounts of both titanium and zirconium, and passing the coremember through the bushing into the crucible.

OBJECTS OF THE INVENTION A primary object of this invention is toprovide an apparatus for continuously casting metal which effectivelyovercomes the entrainment of particles of foreign metals or othermaterials within the cast product, and thereby produces a cast productfree of degrading contaminants.

Another object of this invention is to extend production runs incontinuous casting operations, and reduce downtime for replacement ofparts by providing apparatus including a bushing insert which resistsdeterioration and loss of structural integrity.

. A further object of this invention is to provide for the production ofrelatively pure continuously cast products. which are more amenable tometal working or shaping procedures, and apparatus therefor.

An additional object of this invention is to provide an improved methodof continuously casting metal which produces a cast product free offoreign inclusions.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view of anovel apparatus constructed in accordance with one embodiment of thisinvention, with the core member and cast product shown in elevation;and,

FIG. 2 is an enlarged fragmentary view of a portion of the apparatusshown in FIG. 1 with the core member and the cast product shown inelevation.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawing,a metal core member 10, such as a rod of copper, is continuously passedupwardly through the apparatus of a continuous casting system 12. Thecore member can be moved through the apparatus by appropriate drivemeans such as feed rolls l4 and 14, and take up rolls 16 and 16'. Coremember 10 is preferably first passed through an annular cutting die 18which continuously shaves off a portion of the outer surface area of thecore member to eliminate surface oxides or contaminants and to provide aclean metal face for the adherence of the molten metal. Other means,such as an acid pickling bath, can serve to effectively clean thesurface of the core member. However, the annular cutting die 18 is apreferred means because among other reasons, it also performs a scalingfunction at the system entrance.

Passing from the cutting die 18, the shaved and cleaned core member 10enters a vestibule chamber 20, which is preferably evacuated, such asthrough pipe 22, to minimize exposure of the shaved core member tooxygen and other air borne contaminants.

Crucible 24, comprising a suitable refractory vessel for the containmentof molten metal 26, such as copper, is preferably enclosed to protect iscontents from the atmosphere. Crucible 24 is provided with an entry portor orifice 28 located in its bottom wall 30 below the surface ot itsmolten metal contents for passage therethrough of the core memberupwardly into the crucible chamber interior, and through its contents ofmolten metal 26. A bushing member or insert 32 formed of a refractorymaterial is provided within entry port 28 of crucible 24, and inaccordance with one preferred embodiment of the invention, the bushingmember extends from the vestibule chamber to the crucible 24substantially as shown in the drawing.

In accordance with this invention, bushing member or insert 32, providedfor the passage therethrough of the core member into the crucible, iscomposed of, or formed from, molybdenum metal alloyed with minor amountsof both titanium and zirconium, for example at least about 99 percent byweight of molybdenum with about 0.25 to 1.0 percent by weight oftitanium and about 0.04 to 0.2 percent by weight of zirconium. Inaccordance with the preferred embodiment of the invention, the bushingmember 32 is composed of an alloy consisting essentially of about 0.48percent by weight of titanium and about 0.9 percent by weight ofzirconium, and the balance molybdenum.

It has been discovered that bushings or inlet port inserts composed ofthe aforesaid molybdenum alloys effectively eliminate the occurrence ofinclusions or presence of particles of foreign metal or other materialwithin the cast products derived therefrom. Moreover the bushing memberformed of these alloys have been found to provide exceptionally longerperiods of service life of up to several times greater than priorbushings composed of other refractory materials such as sinteredmolybdenum.

On passing through the bath of molten metal 26 with the apparatus ofthis invention, the relatively cold core member 10 progressivelyaccretes over its surface an accumulation of solidifying melt. The coremember then passes out of the crucible 24 up through an exit port 34 ororifice in the top wall 36 of the crucible 24. Upon exiting from thecrucible chamber, the cast product moves through a water spray 38, orother suitable cooling means to reduce the temperature of the castproduct.

Prior to the above-referenced discovery that the occurrence ofinclusions or bodies of foreign material can be virtually eliminated bythe use of bushing inserts composed of the particular alloys ofmolybdenum, breaks in the drawing of copper wire from cast copper rodsproduced by the dip forming process were a rela tively common occurrencedue to the presence of included particles of foreign material. After theuse of the bushing inserts of the molybdenum alloy in the production ofdip formed continuously cast copper rod, no breaks or interruptionscaused by inclusions or foreign particles were found over a period ofseveral months of wire drawing production, and running time of the wiredrawing production machines was increased about 20 percent.

Molybdenum alloys of the type which are suitable for use in forming thebushing members or inserts of this invention for use in dip formingapparatus and produc- 4 tion, are reported in Alloy Digest, August 1964,Published by Engineering Alloy Digest Inc., Upper Montclair, NJ. Thecompositions of commercial sources of the alloys are given therein asfollows:

Titanium 0.40 0.55 Zirconium 0.06 0.12 Carbon 0.01 0.04 Oxygen 0.0025max. Hydrogen 0.0005 max. Nitrogen 0.002 max. Molybdenum 99.25 min.

Although copper has been mentioned in the foregoing description of anembodiment of this invention, the apparatus and method of this inventionare useful in the casting of other metals. For example, the inventioncan be used in the casting of substantially any metal or alloy upon acore member composed of the same metal or alloy as the melt, or adifferent metal or alloy, and may include plating or encasingoperations.

In addition to overcoming the problem of inclusions, the molybdenumalloy insert of this invention also eliminates some of the causes of theformation of bells which comprise intermittent oveer-accretions orattachments of excessive and irregular accumulations of molten metal onthe moving core member. For instance the molybdenum alloy insertprovides much greater resistance to wetting by the molten copper and inturn adherence and build up of cooled melt adjacent to the core rodpassing through the insert. Moreover the alloys freedom from high oxidecontents eliminates a source of chilling the copper melt in the areaabout the core rod.

Although the invention has been described with reference to certainspecific embodiments thereof, numerous modifications are possible and itis desired to cover all modifications falling within the spirit andscope of this invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A method of continuously casting copper, comprising the steps of:passing a metal core member comprising copperupwardly into and through acrucible containing molten metal comprising copper, said core memberentering the crucible containing molten metal comprising copper througha bushing member consist ing essentially of a molybdenum alloy of atleast about 99 percent by weight of molybdenum and about 0.25 to about1.0 percent by weight of titanium and about 0.04 to about 0.2 percent byweight of zirconium, and thereby accreting and solidifying molten metalcomprising copper on the core member, and removing the metal core memberwith the accreted and solidified molten metal comprising copper thereonfrom the crucible and cooling it.

2. The method of continuously casting of claim 1, wherein the coremember consists essentially of cop per.

3. The method of continuously casting of claim 1, wherein the coremember enters the crucible containing molten metal comprising copperthrough a bushing member of molybdenum alloy containing about 0.40 toabout 0.55 percent by weight of titanium and about 0.06 to about 0.12percent by weight of zirconium.

1. A METHOD OF CONTINUOUSLY CASTING COPPER, COMPRISING THE STEPS OF:PASSING A METAL CORE MEMBER COMPRISING COPPER UPWARDLY INTO AND THROUGHA CRUCIBLE CONTAINING MOLTEN METAL COMPRISING COPPER, SAID CORE MEMBERENTERING THE CRUCIBLE CONTAINING MOLTEN METAL COMPRISING COPPER THROUGHA BUSHING MEMBER CONSISTING ESSENTIALLY OF A MOLYBDENUM ALLOY OF ATLEAST ABOUT 99 PERCENT BY WEIGHT OF MOLYBDENUM AND ABOUT 0.25 TO ABOUT1.0 PERCENT BY WEIGHT OF TITANIUM AND ABOUT 0.04 TO ABOUT 0.2 PERCENT BYWEIGHT OF ZIRCONIUM, AND THEREBY ACCRETING AND SOLIDIFYING MOLTEN METALCOMPRISING COPPER ON THE CORE MEMBER, AND REMOVING THE METAL CORE MEMBERWITH THE ACCRETED AND SOLIDIFIED MOLTEN METAL COMPRISING COPPER THEREONFROM THE CRUCIBLE AND COOLING IT.
 2. The method of continuously castingof claim 1, wherein the core member consists essentially of copper. 3.The method of continuously casting of claim 1, wherein the core memberenters the crucible containing molten metal comprising copper through abushing member of molybdenum alloy containing about 0.40 to about 0.55percent by weight of titanium and about 0.06 to about 0.12 percent byweight of zirconium.